Enjoy the traditional Christmas ham but don't indulge too much if you are an asthmatic.
A new French study, published in journal Thorax, has found that four or more weekly servings of cured and processed meats - such as ham and salami - is linked to worsening asthma symptoms.
Such food products are rich in nitrites, which may have a role in airway inflammation, a typical feature of asthma, say the researchers from the Paul Brousse Hospital in France.
To find out if dietary processed meat intake was associated with the worsening of asthma symptoms over time, the researchers drew on data from participants in the French Epidemiological study on the Genetics and Environment of Asthma (EGEA).
This has been tracking the health through surveys and medical examination of more than 2000 asthma patients, their close relatives, and a comparison group from five cities in France for more than 20 years.
Data on 971 participants obtained between 2011-13 showed there had been no change in asthma symptoms for just over half (53 per cent).
In one in five, symptoms had worsened and in around one in four symptoms had improved.
Among those who ate one or fewer weekly servings, the proportion of those with worsening asthma symptoms was 14%; among those eating 1-4 serves, the proportion was 20 per cent; and among those eating four or more, the proportion was 22 per cent.
After taking account of potentially influential factors, such as smoking, regular physical activity, age, sex, and educational attainment, those who ate the most cured meats were 76 per cent more likely to experience worsening asthma symptoms than those who ate the least.
Obesity, which has previously been linked to worsening asthma, accounted for just 14 per cent of this association, according to the calculations.
This suggests that processed meat intake may have an independent role in asthma symptoms, say the researchers.
Because this was an observational study, the authors note no firm conclusions can be drawn about cause and effect.
